The goal of these studies is to develop new genetic markers for predicting prognosis of breast cancer. It will: 1) utilize subtractive hybridization to find new genes; and 2) further evaluate the significance of an allelic loss at chromosome 1q23-32, first described by this project, with the long- term goal of cloning a putative suppressor gene at this locus. It will also measure the frequency of allelic losses at random genetic loci and/or amplifications to test the hypothesis that the likelihood of a specific genetic alteration conferring aggressive tumor behavior is directly proportional to the overall frequency of genetic aberrations in that tumor. It will examine breast cancers for evidence of aberrant methylation to determine whether abnormal methylation is associated with allelic instability. For selected breast cancer specimens, normal cells (either blood or skin) will be available from the patient and both parents. In these cases, studies will be performed to evaluate the role of maternal imprinting in breast cancer by determining whether the maternal allele is preferentially lost.